In the field of electronic packaging, a molding process and a wafer thinning process are required after a chip-on-wafer (CoW) assembly. Some factors such as size, chip height uniformity, chip distribution uniformity, hardness, rigidity, coefficient of thermal expansion and glass transition temperature of the molding material and chips, warpage of the wafer and warping uniformity influence the product yield.
It has been found that serious warping easily occurs to a molding package during a reflow process and consequently to cause non-contact or separation between a CoW and a substrate. Therefore, how to overcome the above-described drawbacks has become critical.